The present invention concerns a drive system for weaving machines. More particularly, the invention concerns a drive system comprising a pick finding device which makes it possible to achieve a coupling between the auxiliary shaft and the main shaft of a weaving machine whereby the coupling between these shafts can occur at different angular positions and automatically as a function of an adjustable set value. The "main shaft" is the shaft which drives the batten and, in the case of a gripper weaving machine, also drives the weft gripper drive. The main shaft rotates at the weaving machine speed.
The "auxiliary shaft" is the shaft which drives the shed forming device, i.e., the heddle frames and this auxiliary shaft rotates at one-half the speed of the main shaft.
The objective of the present invention is to provide a drive whereby the crossing moment in time of the heddle frames can be modified relatively easily in relation to the beating up moment in time of the batten, whereby such operation takes place automatically as a function of the adjustment carried out by the weaver after having considered the appearance of the woven cloth.
It is indeed already known that the crossing moment of the heddle frames with respect to the heating up moment of the batten is a decisive factor in weaving machines as far as the appearance of the woven cloth is concerned. Consequently, it is necessary to be able to adjust these values, whereby fine adjustment is possible.
According to a well known method, the auxiliary shaft of the weaving machine, which drives the heddle frames, and the main shaft of the weaving machine which drives the batten, can be manually adjusted relative to each other in order to modify the crossing moment of the heddle frames with respect to the beating up moment of the batten. This operaton is achieved, for instance, by means of a pick finding device comprising a belt pulley or of a gear wheel that is rotated with respect to the shaft after loosening the clamp connection or, for instance, by shifting a toothed belt over a few teeth, or, in the case of a gear transmission, by shifting the tooth gears over a few teeth in relationship to each other and to engage them afterwards. Quite obviously, this method involves time losses for these mounting and assembling operations.
It is also well known that methods are designed for pick finding devices whereby the main shaft and the auxiliary shaft are always coupled with each other in locked relationship. In this environment, clutch couplings are used which make coupling possible only for a specific mutual position of the main and auxiliary shafts. Clearly, such pick finding devices have the disadvantage that they do not enable the automatic adjustment of the crossing moment of the heddle frames with respect to the heating up moment of the batten.